Leek and Potato Gratin

I love potatoes au gratin, but I've been guilty of just using the boxes of au gratin potatoes you find in the grocery store. This Easter, I thought I'd try some homemade potatoes. I found this recipe in an Easter flyer from Kroger.
Be sure the potatoes you use are the right type for au gratin baked dishes. Russet potatoes are too fluffy and mealy. Yukon golds, or red potatoes, are firmer and bake well in cream sauces.

Wash, trim, and cut leeks in half lengthwise. Slice thinly, using white and light green parts. Discard dark green parts.
Melt 2 tablespoons butter in a large skillet over medium heat. Add leeks, garlic, remaining salt and pepper, and the whole sprigs of thyme and rosemary. Cook, stirring, until leeks are tender and golden, about 5-7 minutes. Add cream, scraping up browned bits of leeks from the bottom of the pan. Simmer gently for 5 minutes. Remove thyme and rosemary sprigs and discard.

3

Pour the leek-cream mixture over potatoes and top with the Gruyère. Cover dish with aluminum foil and bake for 40 minutes. Uncover and bake until the cheese is bubbling and golden, 10-15 minutes longer. Let cool slightly before serving.